Biometric implant monitors transplant patients for organ rejection

The sensor can continuously monitor an organ’s temperature.

Northwestern University

Researchers at Northwestern University developed a bioelectric implant that can detect temperature fluctuations that typically happen right before a body rejects an organ transplant. The sensor is smaller than a fingernail, and a mere 220 micrometers thick.

This new sensor technology is thin enough to sit directly on a kidney's fibrous layer — called the renal capsule — which surrounds and protects the organ. The device works by continuously monitoring changes to blood flow and temperature. The built-in thermometer can sense increases as minuscule as 0.004 degrees Celsius. Once an irregularity is detected, the sensor, which contains a micro coin cell battery for power, uses Bluetooth to alert a patient or physician via a smartphone or tablet. Any increase typically signals inflammation which is a potential sign of transplant rejection.

After any surgery that involves an organ transplant, the risk of rejection is high. The sensor was developed specifically for kidney transplants but it could also work for other organs, including the liver and lungs. Kidney transplants in the US are on the rise and are usually recommended for people who will not be able to live without dialysis. The American Kidney Fund cites that an acute rejection of a kidney transplant one month after surgery happens in about five to twenty percent of patients that go under.

That’s why it is critical to detect transplant rejection, which occurs when your body's immune system treats the new organ like a foreign object and attacks it. If a healthcare provider detects signs of rejection early enough, medical intervention can preserve the new organ in the new host. Northwestern researchers said that the device detected warning signs of organ rejection three weeks earlier than current monitoring methods. The current “gold standard” for detecting rejection is a biopsy, where a tissue sample is extracted from the transplanted organ and then analyzed in a lab. However, biopsies are invasive and can cause bleeding and increase the risk for infection.

An infrared camera glows red where the thermometer detects a subtle source of heat.
An infrared camera glows red where the thermometer detects a subtle source of heat. (Northwestern University)

Despite developing an innovative first-of-its-kind product, researchers at Northwestern University still have a long way to go. It still needs to be tested on humans in a clinical setting before it can make any impact in the surgical market. Northwestern’s John A. Rogers, a bioelectronics expert who led the device development, said in a statement that his team is now evaluating ways to recharge the coin cell battery so that it can last a lifetime.